Biological Invasions: Aquatic Invasions (14b)

Question 1

How did these fish get here in the first place?

Answer 1

Introduced through legislation encouraging import of angling species for recreational purposes.

Question 2

How did they spread? (5)

Answer 2

South Africa
|
Lesotho
|
Swaziland
|
Zimbabwe
|
Zambia & Mozambique.

Question 3

How have species been moving around?

Answer 3

Via inter-basin transfers (IBWT).

Question 4

SA is a known as what today regarding fish?

Answer 4

Invasive Fish Hotspot.

Question 5

Invasive Fish Hotspots? (3)

Answer 5

• South Africa.
• Australia.
• America.

Question 6

What have been the consequences for these fish introductions? (5)

Answer 6

• Predation by bass has strong effects on minnow distributions (not found when bass arrive).
• Trout has similar impact in cool streams.
• Aliens bring parasites & disease.
• Habit alterations.
• Hybridize with natives (Nile tilapia with Mozambique tilapia).

Question 7

South African minnows features? (4)

Answer 7

• endemic.
• diverse.
• range restricted.
• endangered due to alien species.

Question 8

Result of Nile tilapia on food webs? (3)

Answer 8

• Only top consumer (tertiary consumer) is Nile tilapia (eats 3 fish).
• Reduced secondary consumers.
• Occupy 2 trophic levels due to out competing & replacing natives.

Question 9

How do invasive fishes positively affect people & economy in SA and beyond? (3)

Answer 9

• Source of Recreational anglers.
• Subsistence angling (food security).
• Freshwater aquaculture industry (to sell to the market).

Question 10

Bass fishing in SA? (2)

Answer 10

• Bass anglers are catch & release fanatics.
• Is a sport in SA (BASS Federation Nationals in the USA (SABAA)).

Question 11

How does current SA legislation dictate how we should manage invasive fishes?

Question 12

Managing smallmouth bass in SA?

Answer 12

• Prohibited in natural water bodies (rivers, lakes).
• Allowed in dams with established fisheries.
• CapeNature removed it (successfully) from Rondegat River in 2012 using Piscicide application (fish poison).

Question 13

Implementation conflicts?

Answer 13

• Public outcry from some anglers.
• Solved via stakeholder workshops & EIA.

Question 14

Results of Bass removal? (3)

Answer 14

• 4km of invaded stream is now a new refuge for native fishes.
• Bass anglers were supportive in the end.
• Eradication is a success & sustainable.

Question 15

Other aquatic invasions? (3)

Answer 15

• Aquatic macrophytes.
• Algae.
• Aquatic invertebrates.

Question 16

Impacts of these other aquatic invasions? (4)

Answer 16

• Biodiversity.
• Ecosystem function.
• Economic activity.
• Recreation.

Question 17

Invasion pathways? (5)

Answer 17

• Aquarium trade.
• Ballast water.
• IBWT.
• Hitch-hiking on other introduced species (eg. Tapeworms).
• Hitch-hiking on humans & their personal items.

Question 18

Eg of Hitch-hikers on human belongings?

Answer 18

Didymo/Rock snot.

Question 19

Didymo?

Answer 19

• invasive diatoms.
• Hitch-hikers via human belongings like fishing equipment.

Question 20

Didymo introduction?

Answer 20

Brought to New Zealand in mid-2000s by flyfishermen from North America.

Question 21

Didymo negative impacts? (2)

Answer 21

• Decreases aesthetic appeal.
• Decreases recreational values of streams (via less trout to catch & less anglers).

Question 22

Eg of Hitch-hikers through ballast water?

Answer 22

Killer shrimp.

Question 23

Killer shrimp?

Answer 23

• invasive invertebrate.
• large predatory amphipod.
• kills native amphipods.

Question 24

Killer shrimp introduction?

Answer 24

Dispersed across Europe through shipping canals.

Question 25

Eg of invasive macrophytes?

Answer 25

Water Hyacinth.

Question 26

Water Hyacinth introduction?

Answer 26

Traded as a pond decoration.

Question 27

Water Hyacinth?

Answer 27

• Spreads vegetatively.
• Grows in static, warm water.
• Onstructs water movement.
• highly invasive.

Question 28

Water hyacinth negative impacts? (5)

Answer 28

• Disrupts human use recreationally.
• Restricts boat access.
• Blocks photosynthesis.
• Nutrient depletion.
• Harbour pathogen vectors (mosquitoes).

Question 29

How to control aquatic invasions?

Answer 29

• Mechanical control.
• Chemical control.

Question 30

Chemical control applications?

Answer 30

Herbicides used to control noxious weeds (but are damaging to environment).

Question 31

When is mechanical control used? (2)

Answer 31

• When herbicides are unavailable.
• When herbicides are appropriate.

Question 32

Why are these 2 controls used? (2)

Answer 32

• Short-term solution.
• Only practical solution available.

Question 33

Egs of Biocontrol regarding aquatic Invasions?

Answer 33

• Salvinia = herbivorous insect.
• Eichornia = herbivorous insect.